AC voltammetric carbon paste-based enzyme immunosensors

Carbon paste electrodes, previously anodised in a basic media. are the basi s for the development of a new voltammetric immunosensor device. Passive ad sorption of the appropriate immunochemical reagent was performed onto the e lectrode surface. Alkaline Phosphatase labelled immunoglobulin was the trac er used in this work, 3-indoxyl phosphate being a very suitable enzymatic s ubstrate for the electrochemical detection of the corresponding affinity re action. The hydrolysis of this molecule generates indigo dimmer. This produ ct was detected by alternating current voltammetry taking advantage of the adsorptive and inherent electrodic properties that it exhibits. The same el ectrochemical anodisation was used at the end of one assay to remove the en tire protein layer attached to the carbon paste surface, allowing the forma tion of a new sensing phase and the use of the same support in several cons ecutive experiments. The methodology was applied to the design of two diffe rent immunoassays for the determination of human IgG. Good reproducibility of the electrodic signal and a limit of detection around 10(-10) M were ach ieved. (C) 2000 Elsevier Science S.A. All rights reserved.